SortIndex

Proof of concept to maintain a file with sorted and unique values. This could be helpful for building building indexes.

Range#bsearch is used to determine if a line is already in the file and to determine where a line should be inserted. This means Ruby 2.0 is required.

Add this line to your application's Gemfile:

gem 'sort_index'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sort_index

Use sorted_puts on the File instance instead of write, <<, etc.

SortIndex::File.open('animals', 'w+') do |f|
  f.sorted_puts 'cat'  # add stuff out of order
  f.sorted_puts 'bat'
  f.sorted_puts 'dog'
  f.sorted_puts 'ant'
  f.sorted_puts 'cat'  # duplicate on purpose
end

IO.read('animals')
=> "ant\nbat\ncat\ndog\n"

Performance of writes is probably the biggest problem. There really isn't a great way to insert lines in the middle of a file. So we do it the naive way.

1. save current position IO#tell
2. read the remaining bytes of the file using IO#read
3. write the line at the current position
4. write the rest of the contents from step 2.

Common sense would say don't create gigabyte files this way. Use unix calls instead:

echo 'cat' >> animals
echo 'bat' >> animals
echo 'dog' >> animals
echo 'ant' >> animals
sort -u animals

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/ddrscott/sort_index.

The gem is available as open source under the terms of the MIT License.